cheers OvO, on 2015-September-17, 08:59, said:
It's extremely common to also use double with very strong (18/19 + HCP) hands without support for all suits, in order to limit the range of a simple overcall, intending to introduce spades in this case if partner doesn't bid a major, showing 5+ spades and 18+. This is basic bidding you apparently haven't learned. The scenario you are avoiding by doubling rather than overcalling is 1d-(1s)-all pass when you have game on. Because a one level overcall can be rather weak (7/8 pts), advancer is not going to respond with all 6/7/8 counts like he would if you had opened the bidding, because it's dangerous to jack up the bidding on a possible misfit when both players aren't very strong. Advancer might have a 2524 7 count and have no sensible bid over 1s other than pass, and then you have missed 4H.
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People mentioning 2nt were advocating using it as a conventional raise in competition, analogous to using 2nt as a raise of opener, e.g. 1s-p-2nt, 1s-dbl-2nt. This is a treatment used by some subset of more advanced players. But definitely not something one should assume is in effect.
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Most common is the lowest available cue bid. Jump raise is most popularly used as weak or mixed in competition. SAYC specifically is hard to assume anything though; officially from the pamphlet jump raise of opener is still invitational raise, while after an overcall is completely undefined. But only a small percentage of people claiming to play "SAYC" have actually read the pamphlet, so most probably assume jump raise = weak in comp, and cue is likely safest.